Pulse generator



Sept. 11, 1951 P- C. SHERERTZ PULSE GENERATOR Filed Aug. 24, 1949 gwuwwmPAUL C. SH ERERTZ ATTORNEY Patented Sept. 11,1951

UNITED STATES PATENT OFFICE 2,567,239 PULSE GENERATOR Paul C. Shcrertz,Washingto'mD. C. Application August 24, 1949,, Serial No. 112,161

11 Claims. (01. 315-237) (Granted under the act of March 3, 1883, as

amended April 30,

envelope shape throughout a wide range of pulse repetition frequencies;Moreover, the maximum pulse repetition frequency of the prior pulsegenerators at which the characteristics of the pulses are unaffectedthereby is inherently low. In most pulse applications the operatingefficiency increases with the pulse repetition frequency and it istherefore advantageous to provide means for producing undistorted pulsesat previously unattainable high repetition frequencies.

It is therefore an object of the present inven-- 'tion to provide anovel pulse generator capable of producing a series of fractionalmicrosecond pulses throughout an extremely widerange of pulse repetitionfrequencies.

Another object is to provide a novel generator for producing uniformpulses at a high repetition frequency unattainable by the generators ofthe prior art.

Another object is to provide a novel pulse generator wherein theduration, amplitude and envelope shape of the produced pulses areindependent of the pulse repetition frequency at high repetitionfrequencies as compared to the optimum repetition frequencies of theprior pulse generators.

Still another object of the present invention is to provide a lowimpedance, externally triggered pulse generator including a pulseforming network and a novel charging circuit therefore designed toeliminate the use of passive charging element capable of producingsimilar fractional microsecond pulses throughout a wide range of pulserepetition frequencies.

Still another object is to provide a pulse generator of the typeincluding a pulse forming network charged during the interval betweenpulses 2 pulse repetition frequencies unattainable by the prior artpulse generators. Other objects and features of the present inventionwill appear more fully hereinafter from the following detaileddescription considered in connection with the accompanying drawing whichdiscloses one embodiment of the invention. It is expresslyunderstoodhowever that the drawing is designed for purposes of illustration onlyand not as a definition of the limits of the invention, reference forthe latter purpose being had to the appended claims.- I

The single figure of the drawing disclose a circuit diagram of a pulsegenerator constructed in accordance with the principles of the presentinvention.

Pulse generators of the present invention are of the type including-apulseforming network charged from a source of energy during the intervalbetween pulses which is periodically or aperiodically discharged througha low impedance path to form output pulses. An electron discharge-deviceof the type ofiering a low impedance when conducting, such as a gaseouselectron discharge device, is employed to provide the low impedancedischarge path. In operation, the gaseous electron discharge device isquenched simultaneously with termination of network discharge, with thenetwork charged to a potential above ground corresponding to the cut-01fpotential of the gaseous device, and ionization persists an appreciableperiod of time after the quenching action, thus rendering thegaseouselectron discharge device subject to self-triggeringin response to aslight increase in its anode potential.

Inorder to prevent self-triggering the prior pulse generators employ:passive charging'elements which substantially limit'the higher range ofpulserepetition frequencies without materially affecting the duration,amplitude and envelope shape of the produced pulses. The presentinvention overcomes these limitations by providing a novel chargingcircuit for the pulse forming network including a control circuittherefore operable in accordance with ionization and completede-ionization of the gaseous electron discharge device.

The foregoing is more fully understood with particular reference to thedrawing which discloses a pulse generator including -a pulse formingnetwork in the form of an open ended delay line Ill. The delay line H]is charged from a source of positive potential applied to a terminal ll,through an electron discharge device l2 and a conductor [3. The electrondischarge device ascaeco 3 I2 is connected to function as a cathodefollower for a purpose that will appear more fully hereinafter. Agaseous electron discharge device I4 provides a low impedance path toground for discharge of the delay line In upon ionization thereof inresponse to triggering pulses, such as pulse a, applied to generatorinput terminal I5. Generator output terminal I6 is connected between thelow potential side of the delay line H] and a grounded resistance I!having a value substantially equal to the characteristics impedance ofof the line l0. With the foregoing arrangement, whenever the delay line10 is discharged upon ionization of the discharge device M a, negativepulse 2) is produced at the output terminal [6, the duration, amplitudeand envelope shape of which are determined by the characteristics of thedelay line H).

The gaseous electron discharge device I 4 includes an anode I8 connectedto the conductor i a g ounded cath de s an control lectrod s and 2|respectively coupled to the input termihel I b w o ca a o s Z a d 3- T99 101 ele rode 8 s b ase at und po en by e esis 4 d a ne tive b sipotential is normally maintained on the control electrode 3 b a nne t onh reto. in udi a ot n e mote: 6 and a c n r s stor 21 h a eo i v a e souce 25- Wh e the seous electron d schar e de e t is ionized the co 0 troe ectr de 21 is driv n p sitive to ap roamately ground potential, andthis positive bias persists following quenching of the discharge deride4 noon term n on of d charge current hereth oueh or a perio oi tim drmined by the deionization rate of the gas and the time constant of thecapacitor 23 and the resistor 21.

In order to prevent self-triggering of the gaseous electron dischar e deice [4 in response to ne har n when ion ze s ex s s i he d vice M thepresent invention provides novel means. ier is lat he har n sources fr mhe del ine ii! in e ponse o ionizati n o e d scharg de ic 4 an o.reeestehl -sh ne the cha n circ i i d pe den on o p ete deion etioh o te with n e device I4, with he means cha ac er zed in such a ma ner as toallow the generator to function at a high pulse. repetition f eq ency whut d s o t e pu es ormed b e delay l n e or oin meansincludes thecathode follower l2 and con:- trol means therefor operative inaccordance with th ias on h ont ol electrode 2! of the discharge device{4. The cathode follower l2 ine iide an a ode 28. o ed to. h te minal Ia cathode 29 connected through isolating resistor 30 o the conductor l3,and a control elect-rode 3!. The control means for the cathode follower[2 n udes a e ec on dischar e device 32 which may comprise a hard vacuumtube, having an anode 33 connected to the cathode follower controlelectrode 3i and to the conductor l 3 through a resistor 34, a controlelectrode 35 coupled through a resistor 36 to the control electrode 2|t'the, d sch rge devic it, and a cathode 31 coupled to ground and to thepotentiometer 26 through resistors 38 and 39, respectively. The el ct ondischar devi e. 2 s normally b oc y the ne t ve bia n he controlelectrode 35 nd t e. mo osit ve n a ive. bia on he. oathe es. d rm n d bhe esi a tv 8 and 319, however, when the electron dischar e device H edhe lting osi iv tent l rawn. by. the control electrode 2 sufiicient todrive the le tee'dieehe e e c nt o duc o Lil Upon conduction, the device32 draws current from the line Ill through the resistor 34 andestablishes a blocking bias on the control electrode 3| to interrupt theline charging circuit. Since ionized gas is present in the dischargedevice M for an appreciable period of time following quenching thereof,and since the line In is charged to a certain potential above ground atthe time the device 14 is quenched, the blocking bias is maintained onthe cathode follower I2 until the gaseous device i4 becomes completelydeionized. It is understood that the rate of current flow through thedevice 32 is regulated to maintain the cathode follower 2 blockedthroughout the ionization period of the device I4. Conduction of thedevice 32 also drops the potential of the line It) below the cut-offpotential of the gaseous device l4 and thereby prevents self-triggeringof the device id in response to the abrupt potential increase at theanode l8 mm diat y llowing e min n o ne d charge.

he si t r i n n ce sar r P o er fun ti ni g o e cha g ir t b m bincluded as an isolating impedance to prevent niu y o th d v e i t p orglec t pr vide s mo t e a e bias on he ontrol e ro 2! or i th ev n of at nure n the negative bias supply circuit.

When the pulse generator described heretofore s in its quiescent Sta theas e ec on d scharge device [4 is non-ionized and the cathode follower I2 functions to complete the current rei'he at or de ay ine U o zee tionof the gaseous device M in response to the triggering pulse 1 thepotential of the anode l8 abruptly drops from the normal value thereof teeh nd he to he t nti o t in In t e value several volts above groundpotential equal to the normal conduction potential drop of the gaseousdevice M. This negative pulse travels down the line I0, is reflectedfrom the open end thereof, and, after a period of time equal to W t? thee a of he line it?! he e l ct d. necetive pulse reaches the anode ii}and quenches the gaseous device l4 During'discharge of the dew lay lineID a negative pulse 1 appears at the output terminal 16; the duration,envelope shape, and amplitude of which are determinedby thecharacteristics of the delay line H].

At the instant of ionization the positive potene tial drawn by thecontrol electrode 2| drives the discharge device 32 into conduction todischarge the line H] to ground potential and to blockth'e cathodefollower [2 thereb terminating the flow of charging current to the lineIi). The charging current path remains interrupted until the device l4becomes completely deionized, at which time the control electrode 2!returns to its normal negative bias and terminates the clamping actionof the discharge device 32.

There is thus provided by the present invention a novel pulse generatorcapable of produc ing fractional microsecond pulses, the duration,amplitude and envelope shape of which are solely determined by thecharacteristics of the pulse forming network completely independentofthe pulse repetition frequency which may be varied throughout anextremely wide. range including a high repetition frequency as comparedto the optimum repetition frequencies of the prior pulse generators. Thenovel, use disclosed and described heretoforel of a gaseous electrondischarge device, including a control electrode for developing a controlvoltage in dependency on ionization and a icathode follower ifrthe pulseforming-network charging circuit operable in aecordancewith the controlvoltage through a clamping tube which also functions to reduce thenetworkgpotential belowthe cut-off potential of the gaseous dischargedevice, provides a pulse generator capable of the foregoing operationwherein pulses having characteristics solely de; termined by the pulseforming network are produced at high pulse repetition frequenciesunattainable by pulse generators of the prior art. In actual practicepulse generators of the present invention have produced uniform,undistorted 100 voltpulse of fractional microsecond duration throughouta wide range of pulse repetition frequencies up to 3500 pulses persecond. Moreover, pulse generators of the present invention areinherently low impedance circuits and may be coupled to driven circuitswithout distortion.

Although only one embodiment of the present invention has been disclosedand described herein it is expressly understood that various changes andsubstitutions ma be made therein without departing from the spirit ofthe invention as well understood by those skilled in the art. Referencetherefore will be had to the appended claims for a definition of thelimits of the invention.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

1. In a pulse generator having a pulse forming network, a cathodefollower means coupled to said network for charging the same, and a lowimpedance discharge means coupled to said network for discharging thesame through a load circuit.

2. In a pulse generator having a pulse forming network, a cathodefollower means coupled to said network for charging the same, and anionizable electron discharge device coupled to said network fordischarging the Same through a load circuit upon ionization thereof.

3. In a pulse generator having a pulse forming network, a cathodefollower means coupled to said network for charging the same, anionizable electron discharge device coupled to said network fordischarging the same through a load circuit upon ionization thereof, andblocking means coupled to said cathode follower means and responsive tothe ionization of said discharge device for rendering said cathodefollower means ineffective to charge said network,

4. In a pulse generator having a pulse forming network, a charging meanscoupled to said network, an ionizable electron discharge device coupledto said network for discharging the same through a load circuit uponionization thereof, and means coupled to said discharge device andresponsive to ionization thereof to render said charging meansinefiective to charge said network.

5. In a pulse generator having a pulse forming network, charging meanscoupled to said network, an ionizable electron discharge device coupledto said network for discharging the same through a load circuit uponionization thereof, a normally non-conducting electron discharge devicecoupled to said ionizable discharge device and responsive to ionizationthereof to be rendered conductive, and means responsive to conduction ofsaid normally non-conducting discharge device for rendering saidcharging means ineffective to charge said network. N f

6. A pulse generator comprising a charged operi ended delay line, agaseous electron discharge device connected to said line to provide alow impedance discharge path therefore, tri ger means for,-ionizing saidgaseous electron dis-" charge device, a charging circuit for said lineincluding a normally conducting cathode follower forming a conductivepath betweenasource of charging energy and said line, and means forblocking said cathode follower in dependency on the presence of ionizedgas in said gaseous electron discharge device. j--

7. A pulse generator comprising an open ended delay line, a chargingcircuit including a source of currentand a normally conducting cathodefollower feeding said line, a gaseous electron discharge deviceproviding a low impedance path to ground for said line when ionized inresponse to external control pulses, means associated with said devicefor producing a control voltage in dependency on ionization of saiddevice, and clamping means operable in accordance with said controlvoltage for applying a blocking bias to said cathode follower tointerrupt charging current to said line.

8. A pulse generator comprising an open ended delay line, a chargingcircuit including a source of current and a normally conducting cathodefollower feeding said line, a gaseous electron discharge device fordischarging said line to a potential equal to the cut-off potential ofsaid device when ionized in response to a control signal, meansproducing a control voltage in dependency on ionization of said device,and means including an electron discharge device operative in responseto said control voltage for blocking said cathode follower in accordancetherewith to interrupt charging current to said line and for dischargingsaid line to a potential value below the cut-off potential of saiddevice.

9. A pulse generator comprising an open ended delay line, a chargingcircuit including a source of current and a normally conducting cathodefollower feeding said line, a gas filled electron discharge deviceincluding an anode connected to said line, a grounded cathode and anormally negatively biased control electrode drawing positive potentialin response to ionization of said gas, an electron discharge devicehaving an anode connected to said line through a resistance, anegatively biased cathode and a control electrode coupled to the controlelectrode of said gas filled device, and means utilizing the voltagedrop developed across said resistance upon conduction of said electrondischarge device in accordance with ionization of said gas to controlsaid cathode follower.

10. A pulse generator comprising an open ended delay line having anoutput circuit coupled thereto, a charging circuit including a source ofcurrent and a normally conducting cathode follower feeding said line, agas-filled electron discharge device having an anode fed from saidcathode follower through an isolating impedance, a grounded cathode anda control, electrode normally biased negative with respect to ground, avacuum tube having an anode connected to said line through a resistance,a negatively biased cathode and a control electrode coupled to thecontrol electrode of said gas-filled device, means ionizing the gas ofsaid gas-filled device to discharge said line to a potential aboveground corresponding to the cut-off potential of said glas -filleddevice and to drive the control electrode thereof sufliciently positivein response to the presence of ionized gas for rendering said vacuumtube'conducting so that a voltage drop appears across said resistanceand said line is discharged through said vacuum tube to a potential lessthan the cut-off potential of said gas-filled device, and meansemploying said voltage drop to block'said cathode follower and interruptcharging current to said line throughout the presence of ionized gas insaid gas-filled device.

11. A pulse generator having a pulse forming network, a cathode followermeans coupled to said network for charging the same, an ionizableelectron discharge device coupled to said network for discharging thesame through a load circuit upon ionization thereof to a potential equalto the cut-off potential or said device when ionized, and means coupledto said cathode follower means and said network and responsive to theionization of said discharge device for rendering said cathode followerinefiective to charge said network and for discharging said network to apotential below the cut-ofi potential of said device.

PAUL C. SHERERTZ.

REFERENCES CITED FOREIGN PATENTS Name Date Knowles Feb. 2, 1943 Number

